The goal of this proposal is to evaluate the role of the alphal and alpha5 GABAA receptor subunits in EtOH reinforcement. To accomplish this, the high alcohol drinking (HAD) rat lines, the alphal knock out (KO) mice and their wild type counter part (WT) will be used. The first hypothesis to be tested is whether postsynaptic alpha1 receptors in the ventral pallidum (VP) of HAD rats contribute to the reinforcing properties of EtOH. Site-specific microinjection of selective alphal antagonists in the VP will be evaluated for their capacity to attenuate EtOH-maintained responding. It is hypothesized that the alphal antagonist will selectively decrease EtOH responding since the alphal subunit is present in very high levels throughout the VP. The second hypothesis will evaluate the degree to which complete deletion of the alphal subtype modulates acquisition of alcohol-seeking behaviors using the KO and WT mice. It is hypothesized that the KO mice will initiate alcohol-maintained responding because alcohol reward has been shown to be regulated by multiple neurotransmitter systems; however, the drinking in the KO mice is predicted to be significantly lower than the WT. Moreover, we hypothesize that the magnitude of reduction with alphal antagonists in the KOs will be less than that seen in the WT because the KOs will be devoid of a functional alphal subunit. The third specific aim will test the hypothesis that enhanced alphal binding selectivity, longer lived in vivo and more water soluble ligands will result in a more optimal alcohol antagonist. Finally, the fourth hypothesis will assess whether alpha5 receptors in the hippocampus (CA1 and CA3) modulate putative GABAergic EtOH reward substrates (e.g., nucleus accumbens, basal amygdala, bed nucleus of the stria terminalis). To accomplish this, microinjection of selective alpha5 inverse agonists in the hippocampus to attenuate EtOH-maintained responding will be evaluated. We hypothesized that the alpha5 ligands will selectively decrease EtOH responding in the hippocampus since the alpha5 containing receptors are primarily localized in the hippocampus. In contrast, the selective alpha5 ligands infused in the VP will not alter EtOH responding, since this locus is completely devoid of alpha5 subunits, and the ligands have a very low affinity for the alphal receptor subtype. These studies should further our understanding of the GABAA receptor mechanisms in EtOH-seeking behavior and may possibly identify agents which may have potential in reducing alcohol drinking in humans.